Influence of Suction on Mass Loss of Compacted Clayey Soil from the Guabirotuba Formation in Southern Brazil

Compacted soils are vital in constructing unpaved roads and embankments for infrastructure projects, requiring a thorough understanding of how different soil properties influence erosion. This research examined the influence of suction on the mass loss of clayey soil from the Guabirotuba Formation, compacted at various degrees of saturation and densities. The study involved initial physical–chemical, mineralogical, and morphological soil characterization. Tests were then conducted to determine the soil water characteristic curve, hydraulic conductivity, and erodibility using the filter paper method, permeability tests, and the Inderbitzen test. Samples were compacted to dry unit weights of 14.55 kN/m 3 , 15.42 kN/m 3 , and 16.28 kN/m 3 with saturation levels of 20%, 50%, 91.08%, 93.49%, and 95.60%. Results showed that variations in soil density altered the soil water characteristic curve, tending towards a unimodal shape with reduced void ratios. Soil permeability decreased in the desaturation zone of the curve. The study determined that soil mass loss is primarily influenced by saturation degree and density, with saturation emerging as the most crucial factor. Erosion resistance was observed to be lowest at 50% saturation compared to both 20% and optimal saturation levels, which was associated with a reduction in the unsaturated permeability coefficient. It has been found that the influence of slope is negligible. Therefore, soil saturation levels significantly affect erosion resistance, making the soil more susceptible to disruption when air continuously occupies the pore space.